Generally, thermoplastic resins are used in various fields, and methods of use in combination with other resins and the like are attempted when sufficient performance cannot be achieved by the uniform resin. Particularly, a polymer material having elastomer-like characteristics is used in combination therewith in most cases for improving impact resistance. The polymer material used for such purposes is referred to as an impact modifier.
There are proposed compositions obtained by combining, for example, a vinyl chloride resin with chlorinated polyethylene, an ethylene-vinyl acetate copolymer, a methyl methacrylate-butadiene-styrene copolymer (MBS resin), an acrylonitrile-butadiene-styrene copolymer (ABS resin), a butyl acrylate-methyl methacrylate copolymer or the like; a methacrylic resin with a butyl acrylate-styrene-methyl methacrylate copolymer or the like; a polycarbonate resin with an acrylonitrile-butadiene-styrene copolymer (ABS resin), a butyl acrylate-methyl methacrylate copolymer or the like; and a poly(butylene terephthalate) resin with an acrylonitrile-butadiene-styrene copolymer (ABS resin), an epoxy modified ethylene-propylene copolymer or the like. Many of these compositions are industrially utilized.
Among these impact modifiers, a methyl methacrylate-butadiene-styrene copolymer (MBS resin), an acrylonitrile-butadiene-styrene copolymer (ABS resin) and a butyl acrylate-methyl methacrylate copolymer are copolymers obtained by graft copolymerization of a vinyl monomer (forming a shell part) in the presence of cross-linked rubber particles (forming a core part), which are called a core-shell graft copolymer based on the particle structure and are useful as an impact modifier. Among these core-shell graft copolymers, MBS resin and ABS resin obtained by copolymerizing butadiene have a problem of weatherability because unsaturated double bonds remain in the main chain of the polymer. Therefore, a butyl acrylate-methyl methacrylate copolymer is selected very frequently when weatherability is required. It is pointed out, however, that these core-shell graft copolymers have problems of molding flowability because they contain a cross-linked structure though they are useful as an impact modifier.
On the other hand, it is known that a block copolymer obtained by combining a hard segment and a soft segment (rubber component) can be used as a composition by combining the copolymer with a thermoplastic resin. As the block copolymer, a styrene-butadiene copolymer, a styrene-isoprene copolymer and hydrogenated copolymers thereof (referred to as a styrene-ethylene-butylene copolymer and a styrene-ethylene-propylene copolymer, respectively) are widely used. Generally, when these block copolymers are used, a composition having excellent balance of impact resistance, rigidity and molding flowability can be obtained but thermoplastic resins are limited to low-polar resins such as polystyrene resins, polyolefin resins and poly(phenylene ether) resins.
Recently, it is known that a block copolymer containing a methacrylic polymer and an acrylic polymer functions as an excellent impact modifier, and a thermoplastic resin composition excellent in impact resistance can be obtained by combining it with a thermoplastic resin. As the thermoplastic resin to be combined in this case, a high-polar resin such as a poly(vinyl chloride) resin, a poly(methyl methacrylate) resin, a polycarbonate resin, a polyester resin, or a polyamide resin is effective. However, in the acrylic block copolymers, there has not yet been known a means to control physical property balance by introducing a point of reaction with a resin or the like and thus to improve the performance. Therefore, it has been strongly desired to develop the means.
Furthermore, recently, although the above-described block copolymer obtained by combining a hard segment and a soft segment has been used as a thermoplastic elastomer, there is a considerable restriction on an upper temperature limit in use.
Therefore, improvement of physical properties including oil resistance, control of physical property balance, and the like are sometimes required.
A block copolymer having a methacrylic polymer block and an acrylic polymer block is known to function as a thermoplastic elastomer, but there are similar problems. However, there has not yet been known a means to control physical property balance by compounding the copolymer with a specific resin or introducing a point of reaction with a resin or the like and thus to improve the performance. Therefore, it has been strongly desired to develop the means.